Recently there have been many advances in the development of polymeric systems for delivering drugs. However, nearly all of these systems release drugs at decreasing or, at best, constant rates. Prior to this invention there has been no satisfactory means for increase in the release rates on demand nor has there been any way to control drug administration externally from the body once the release process has commenced from the implanted polymer-drug composition. It has been proposed to magnetically modulate drug delivery from implanted polymer-drug compositions by utilizing a composition that includes small magnetic beads imbedded in the polymer together with the drug. Release rates can be enhanced when desired by a oscillating external magnetic field. However, the extent to which release rates of the drug can be increased by the magnetic field has been unduly limited so that it is difficult to apply such a system to a patient who requires a relatively large dosage of drug within a short period of time.
Constant rate delivery also may not be sufficient to deliver drugs in a way that will closely resemble a homeostatic process. This situation is particularly acute in the case of insulin administration for the diabetic. In diabetes mellitus, augmented insulin delivery is required for short time periods after meal consumption.
Accordingly, it would be highly desirable to provide a means for rapidly delivering drugs in vivo from an implant. It would be desirable to provide such a drug delivery system which is capable of delivering the drug at much higher rates than is available from present drug delivery systems.